(a) Field of the Invention
The present invention relates to polyester fiber that can be used as fabric for an airbag, specifically to high strength, high elongation and low Young's modulus polyester fiber having excellent mechanical properties, flexibility, dimensional stability, and the like, a method for preparing the same, and fabric for an airbag using the same.
(b) Description of the Related Art
In general, an airbag refers to a device that protects a driver and a passenger by sensing crash impact applied to a car at frontal crash of a car driving at a speed of about 40 km/h or more, and then, exploding gunpowder to supply gas in the airbag and expand it.
Properties required as fabric for an airbag includes low air permeability for smooth deployment at crash, high strength, high heat resistance for preventing damage and burst of an airbag itself, and flexibility for reducing impact applied to a passenger.
Particularly, an airbag used in an automobile is manufactured in a specific form, and then, to minimize the volume, it is installed on a car handle, side glass window or side structure, and the like in a folded state and maintains the folded state, and when an inflator is operated, it is allowed to expand and deploy.
Therefore, to effectively maintain foldability and packing of the airbag when installed in an automobile, prevent damage or burst of the airbag itself, exhibit excellent airbag cushion deployment performance, and minimize impact applied to a passenger, it is very important that the airbag fabric should have excellent mechanical properties and foldability as well as flexibility for reducing impact applied to a passenger. However, airbag fabrics that may maintain excellent air cut-off effect and flexibility for the safety of a passenger, sufficiently tolerate impact applied to the airbag, and be effectively installed in an automobile have not been suggested yet.
In the prior art, polyamide fiber such as nylon 66, and the like have been used as the material for yarn for an airbag. Although the nylon 66 has excellent impact resistance, it has decreased moisture heat resistance, light resistance, and dimensional stability compared to polyester fiber, and has high raw cost.
Meanwhile, Japanese Patent Laid-Open Publication No. 04-214437 suggested use of polyester fiber for reducing the above defects. However, if an airbag is manufactured using the existing polyester fiber, when installed in an automobile, packing in a small space is difficult due to high stiffness, excessive heat shrinkage may be generated by high temperature heat treatment due to high elasticity and low elongation, and there is a limit in maintaining sufficient mechanical properties and deployment performance under sever conditions of high temperature high moisture.
Accordingly, there is a need for development of fiber that may maintain excellent mechanical properties and air cut-off effect suitable for use as fabric for an airbag, and maintain flexibility for reducing impact applied to a passenger, packing and excellent mechanical properties under sever conditions of high temperature high moisture.